The present invention relates generally to transmitting voice information and in particular, to a method and apparatus for transmitting voice information within a communication system.
Within cellular communication systems, voice quality is often perceived by the user as the most important attribute to any call. Cellular providers along with equipment manufacturers continuously strive to improve voice quality within cellular communication systems. A trade off in voice quality exists in that usually a higher quality voice channel requires more Radio Frequency (RF) capacity, limiting the total number of calls a system can simultaneously provide.
Recently it has been proposed to add dispatch capabilities to the cdma2000 system. Unlike the interconnect services provided by today""s cellular systems, dispatch services have been traditionally provided by two-way radio systems. Such services allow a user to communicate in ways that are difficult or costly using today""s cellular systems. The dispatch group call service, for example, enables a user to communicate with a group of people simultaneously and instantaneously, usually just by depressing a push-to-talk (PTT) button. Using a cellular system, such a call could not occur instantaneously since either telephone numbers would need to be dialed for a three-way call or arrangements would need to be made to setup a conference call.
Likewise, the dispatch individual (typically called a private call) call service enables a user to communicate with another user quickly and spontaneously. This feature is ideal for two people who are working together but are unable to speak with one another directly such as two people working in concert but in different parts of a building. Where a wireless telephone call is more appropriate for a conversation, short messages between two people as they work are better facilitated by the dispatch individual call service.
In addition to voice quality, low delay is also a critical factor in any dispatch call. For example delay that is acceptable for a typical interconnect voice call, can be unacceptable for dispatch services which rely on a very fast connection being made to the called party. Therefore, a need exists for a method and apparatus for transmitting voice information in a dispatch environment that provides acceptable voice quality, yet allows for fast interconnections required by dispatch users.